Atmospheric Science And Air Pollution

chapter 13

Earth’s atmosphere

Weather, climate, and atmospheric conditions

Outdoor pollution and solutions

Stratospheric ozone depletion

Acidic deposition and consequences

Indoor air pollution and solutions

Chapter Outline:

CENTRAL CASE STUDY: L.A. AND ITS SISTER CITY, TEHRAN, STRUGGLE FOR A BREATH OF CLEAN AIR

Vehicles caused smog in Los Angeles from 1970s to 1990s

Policies and technologies improved its air qualities

But its “sister cities” are not as clean

Tehran, Iran, is very polluted

Old cars use cheap gas

Topography, immigration, etc., make things worse

Air pollution kills

3,600/month in Tehran

THE STRUCTURE AND COMPONENTS OF THE ATMOSPHERESection 1

THE ATMOSPHERE

Atmosphere: the thin layer of gases around Earth

Provides oxygen

Absorbs radiation and moderates climate

Transports and recycles water and nutrients

78% N2, 21% O2

Over history, the atmosphere has changed

Human activity is now changing the amount of some gases

CO2, methane (CH4), ozone (O3)

THE ATMOSPHERE’S COMPOSITION

THE FIRST LAYER OF THE ATMOSPHERE

Earth’s four atmospheric layers have different

Temperatures

Densities

Composition

Troposphere: bottommost layer (11 km [7 miles])

Responsible for Earth’s weather

The air gets colder with altitude

Tropopause: the boundary that limits mixing between the troposphere and stratosphere

THE 3 HIGHER LEVELS OF THE ATMOSPHERE

Stratosphere: 11–50 km (7–31 mi) above sea level

Drier and less dense, with little vertical mixing

Gets warmer with altitude

Ozone layer: blocks UV radiation

Mesosphere: low air pressure

Gets colder with altitude

Thermosphere: top layer

SOLAR ENERGY CAUSES AIR TO CIRCULATE An enormous amount of energy from the sun hits Earth

70% is absorbed by water, evaporating the water

Air near Earth’s surface is warm and moist

Convective circulation: less dense, warmer air rises

Creating vertical currents

Rising air expands and cools

Cool air descends and becomes denser

Replacing rising warm air

Convection influences weather and climate

THE ATMOSPHERE DRIVES WEATHER AND CLIMATE

Weather and climate involve physical properties of the troposphere

Temperature, pressure, humidity, cloudiness, wind

Weather: atmospheric conditions within small geographic areas, over short time periods (hours, days)

Climate: patterns of atmospheric conditions across large geographic regions over long periods of time

Mark Twain said, “Climate is what we expect; weather is what we get”

CIRCULATION SYSTEMS PRODUCE CLIMATE PATTERNS

Convective currents contribute to climatic patterns

Hadley cells: convective cells near the equator

Surface air warms, rises, and expands

Causing heavy rainfall near the equator

Giving rise to tropical rainforests

Currents heading north and south are dry

Giving rise to deserts at 30 degrees

Ferrel cells and polar cells: lift air and create precipitation at 60 degrees latitude north and south

Conditions at the poles are dry

GLOBAL WIND PATTERNS

Atmospheric cells interact with Earth’s rotation to produce global wind patterns

As Earth rotates, equatorial regions spin faster

Some areas of the planet’s surface move more quickly than other areas

Coriolis effect: the apparent north–south deflection of air currents of the convective cells

Results in curving global wind patterns

Global wind patterns helped ocean travel by wind-powered sailing ships

CLIMATE PATTERNS AND MOISTURE DISTRIBUTION

STORMS POSE HAZARDS

Atmospheric conditions can produce dangerous storms

Hurricanes (typhoons, cyclones): form when winds rush into areas of low pressure

Warm, moist air over the topical oceans rises

Drawing up huge amounts of water vapor

Which falls as heavy rains

Tornadoes: form when warm air meets cold air

Quickly rising warm air forms a powerful convective current (spinning funnel)

WE NEED TO UNDERSTAND THE ATMOSPHERE

Understanding how the atmosphere works helps us to:

Predict violent storms and protect people

Comprehend how pollution affects climate, ecosystems, economies, and human health

TEMPERATURE INVERSIONS AND AIR QUALITY

Section 2

THERMAL (TEMPERATURE) INVERSION

Thermal inversion: a layer of cool air forms beneath warm air

Inversion layer: the band of air where temperature rises with altitude

Dense, cool air at the bottom of the layer resists mixing

Inversions trap pollutants in cities surrounded by mountains

• Tropospheric air temperature decreases with height– Warm air rises, causing

vertical mixing

TEMPERATURE INVERSIONS Trap air pollutants such as

smog

Can cause freezing rain

Will result in poor air quality and Ozone Alert Days

http://www.airnow.gov

ATMOSPHERIC POLLUTANTS

Section 3

OUTDOOR AIR POLLUTION

Air pollutants: gases and particulate material added to the atmosphere

Can affect climate or harm people or other organisms

Air pollution: the release of pollutants

Outdoor (ambient) air pollution: pollution outside

Has recently decreased due to government policy and improved technologies in developed countries

Developing countries and urban areas still have significant problems

Greenhouse gas emissions may be our worst problem

NATURAL SOURCES CAN POLLUTE

Humans make impacts worse

Farming, grazing cause erosion, desertification

Fire suppression leads to worse fires(dead trees,etc build up on forest floor)

• Fires generate soot and gases

• Winds send huge amounts of dust aloft– Even across oceans

• Volcanoes release particulate matter, sulfur dioxide

WE CREATE OUTDOOR AIR POLLUTION

Humans generate many types of air pollution

Point sources: specific spots where large quantities of pollutants are discharged (power plants)

Non-point sources: more diffuse, consisting of many small, widely spread sources (automobiles)

Primary pollutants: directly harmful or can react to form harmful substances (soot and carbon monoxide)

Secondary pollutants: form when primary pollutants react with constituents of the atmosphere

POLLUTANTS EXERT LOCAL AND GLOBAL EFFECTS Residence time: the time a pollutant stays in the atmosphere

Pollutants with brief residence times exert localized impacts over short time periods

Particulate matter, automobile exhaust

Pollutants with long residence times exert regional or global impacts

Greenhouse gases

Ozone destroyers

LEGISLATION ADDRESSES POLLUTION

The Clean Air Act (1963, amended in 1970, 1990)

Funds research for pollution control

Sets standards for air quality, limits on emissions

Allows citizens to sue parties violating the standards

Introduced a cap-and-trade program for sulfur dioxide

The EPA sets standards for emissions and pollutants

States monitor air quality

They develop, implement, and enforce regulations

They submit plans to the EPA for approval

The EPA takes over enforcement if plans are inadequate

WRAP UP:

1. What is a temperature inversion?

2. How can this affect air quality?

3. Why do the pollutants stay trapped and close to the ground during an inversion?

4. What is the difference between a point and non-point pollutant?

5. Give an example of an air pollutant with a short residence time?

6. Does the residence time affect how we monitor the pollutant?

CRITERIA POLLUTANTS

Section 5

CRITERIA POLLUTANTS: CARBON MONOXIDE

Criteria pollutants: especially great threats to humans

Carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, lead

127 million Americans live in areas that violate standards for at least one criteria pollutant

Carbon monoxide (CO): colorless, odorless gas

Produced primarily by incomplete combustion of fuel

From vehicles and engines, industry, waste combustion, residential wood burning

Prevents blood hemoglobin from binding with oxygen

CRITERIA POLLUTANTS: SO2 AND NOX

Sulfur dioxide (SO2): colorless gas with a strong odor

Coal emissions from electricity generation, industry

Can form acid deposition

Nitrogen dioxide (NO2): foul-smelling red-brown gas

Contributes to smog and acid deposition

Nitrogen oxides (NOx): formed when nitrogen and oxygen react at high temperatures in engines

Vehicles, electrical utilities, industrial combustion

CRITERIA POLLUTANTS: TROPOSPHERIC OZONE

Tropospheric ozone (O3): a colorless gas

A secondary pollutant created from sunlight, heat, nitrogen oxides, volatile carbon-containing chemicals

A major component of smog

Participates in reactions that harm tissues and cause respiratory problems

The pollutant that most frequently exceeds EPA standards

CRITERIA POLLUTANTS: PARTICULATE MATTER ANDLEAD

Particulate matter: suspended solid or liquid particles

Damages respiratory tissue when inhaled

Primary pollutants: dust and soot

Secondary pollutants: sulfates and nitrates

From dust and combustion processes

Lead: in gasoline and industrial metal smelting

Bioaccumulates and damages the nervous system

Banned in gasoline in developed, but not in developing, countries

AGENCIES MONITOR EMISSIONS

State and local agencies monitor and report to the EPA emissions of:

Carbon monoxide, sulfur dioxide, particulate matter, lead, and all nitrogen oxides

Tropospheric ozone, a secondary pollutant, has no emissions to monitor

Agencies monitor volatile organic compounds (VOCs):

Emitted by engines and industrial processes

VOCs can react to produce ozone

U.S. AIR POLLUTION

In 2008, the U.S. emitted 123 million tons of the six monitored pollutants

WE HAVE REDUCED U.S. AIR POLLUTION Total emissions of the six monitored pollutants have declined 60% since the

Clean Air Act of 1970

Despite increased population, energy consumption, miles traveled, and gross domestic product

WE HAVE REDUCED EMISSIONS

Federal policies and technology

Cleaner-burning engines and catalytic converters

Reduced SO2 emissions

Permit trading programs and clean coal technologies

Scrubbers: chemically convert or physically remove pollutants before they leave smokestacks

Phaseout of leaded gasoline

WE STILL HAVE MORE TO DO…

The reduction in outdoor air pollution since 1970 is one of our greatest accomplishments!

Saving the lives of 200,000 Americans since 1970

There is room for improvement:

Concerns over new pollutants and greenhouse gas emissions

U.S. carbon dioxide emissions increased 44% (1970–2008)

The Supreme Court ruled that the EPA could regulate carbon dioxide as a pollutant

There is formidable political opposition to this

TOXIC SUBSTANCES POSE HEALTH RISKS

Toxic air pollutants: substances that cause …

Cancer, reproductive defects, or neurological, immune system, developmental, or respiratory problems

The EPA regulates 188 toxic air pollutants

Including mercury, VOCs, methylene chloride

Toxic air pollutants cause 36 cancer cases per 1 million people

Clean Air Act regulations helped reduce emissions by more than 35% since 1990

INDUSTRIALIZING NATIONS SUFFER INCREASING POLLUTION

Outdoor pollution is getting worse in developing nations

Polluting factories and power plants, increasing numbers of cars

Emphasize economic growth, not pollution control

People burn traditional fuels (wood and charcoal)

China has the world’s worst air pollution

Coal burning, more cars, power plants, factories

Causing over 300,000 premature deaths/year

China is reducing pollution (closing factories, cleaner fuels, raising efficiency standards, cleaner energy, etc.)

POLLUTION IN DEVELOPING NATIONS IS HIGH

In Tehran, vehicles emit 5,000 tons of pollutants each day!

SMOGSection 6

SMOG: OUR MOST COMMON AIR QUALITY PROBLEM

Smog: an unhealthy mixture of air pollutants over urban areas

Industrial smog: burning coal or oil releases

CO2, CO, soot, mercury, sulfur

Sulfuric acid is formed

Regulations in developed countries reduced smog

Coal-burning industrializing countries faces health risks

Due to lax pollution control Smog in Donora, PA, killed 21 people and

sickened 6,000

PHOTOCHEMICAL (BROWN AIR) SMOG Sunlight drives a chemical reactions between primary pollutants and

atmospheric compounds

Forming ozone, NO2, and many other compounds

Appears as a brownish haze

Formed in hot, sunny cities surrounded by mountains

Morning traffic releases NO and VOCs

Irritates eyes, noses, and throats

In 1996, photochemical smog

killed 300 and sickened 400,000 in

5 days

Industrial smog Photochemical smog

Creation of smog

WE CAN REDUCE SMOG

Pollution control technology

Vehicle inspection programs

Financial incentives to replace aging vehicles

Restricting driving

Cleaner burning fuels

Cleaner industrial facilities

Close those that can’t improve

Pollution indicator boards

But…increased population and

cars can wipe out advances

WRAP UP:

1. Which compound is the primary component of photochemical smog?

2. How does smog form?

3. How can we reduce this type of air pollution?

4. Why are some areas, such as Mexico City, more susceptible to smog?

STRATOSPHERIC OZONESection 7

Do Now:1. Which color represents 2013?2.How does 2013 compare with the last 10 years?3.When is the Ozone hole the biggest?4. Why isn’t January to June on the chart?

TAKEN WITH THE OMI INSTRUMENT ON THE AURA SATELLITE

How does the ozone hole change?

SYNTHETIC CHEMICALS DEPLETE STRATOSPHERIC OZONE Ozone in the lower stratosphere absorbs the sun’s

ultraviolet (UV) radiation

UV radiation can damage tissues and DNA

Ozone-depleting substances(ODS): human-made chemicals that destroy ozone

Halocarbons: human-made compounds made from hydrocarbons with added chlorine, bromine, or fluorine

Chlorofluorocarbons (CFCs): halocarbons used as refrigerants, in fire extinguishers, in aerosol cans, etc.

They stay in the stratosphere for a century

CFCS DESTROY OZONE Sunlight releases chlorine atoms that

split ozone

Ozone hole: decreased ozone levels over Antarctica

Discovered in 1985

Measured in Dobson Units

One chlorine atom can destroy 100,000 ozone

molecules

Sept 24, 2006

THE MONTREAL PROTOCOL Montreal Protocol (1987): 196 nations agreed to cut

CFC production in half by 1998

Later agreements deepened cuts, advanced timetables, and addressed other ozone-depleting chemicals

Industry shifted to safer alternative chemicals

We stopped the Antarctic ozone hole from getting worse

Challenges still face us

CFCs will remain in the stratosphere for decades

It can serve as a model for international environmental cooperation

THE OZONE LAYER HAS STOPPED GROWING

Phasing out ozone-depleting substances in 1987 worked—the Antarctic ozone hole has stopped growing

ACID DEPOSITION AND ACID RAINSection 8

ACID DEPOSITION

Acid deposition is another transboundary issue

Acid deposition: the deposition of acid, or acid-forming, pollutants from the air onto Earth’s surface

From automobiles, electric utilities, industrial facilities

Acid rain: precipitation containing acid

Rain, snow, sleet, hail

Atmospheric deposition: the wet or dry deposition of pollutants (mercury, nitrates, organochlorines, etc.)

BURNING FOSSIL FUELS PRODUCES ACID RAIN Burning fossil fuels releases sulfur dioxide and nitrogen oxides

These compounds react with water, oxygen, and oxidants to form sulfuric and nitric acids

IMPACTS OF ACID DEPOSITION

Nutrients are leached from topsoil

Soil chemistry is changed

Toxic metal ions (aluminum, zinc, etc.) are converted into soluble forms that pollute water

Affects surface water and kills fish

Damages crops

Erodes stone buildings, corrodes cars, erases writing on tombstones

PH VALUES OF PRECIPITATION IN THE U.S.

Regions of greatest acidification are downwind of heavily industrialized sources of pollution

WE HAVE BEGUN TO ADDRESS ACID DEPOSITION

The Clear Air Act (1990) established an emissions trading program for sulfur dioxide

Benefits outweighed costs 40:1

New technologies such as scrubbers have helped

Policies and regulations have lowered U.S. emissions of sulfur and nitrogen oxides 43% since 1989

Acid deposition is worsening in the developing world

Coal-burning China emits the most sulfur dioxide and has the world’s worst acid rain problem

WRAP UP

1. How does acid rain form? 2. Where is acid rain most

concentrated? What have we done about it?